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Cisco ONS 15454 SDH Reference Manual, R5.0
April 2008
Chapter10 Circuits and Tunnels
10.12 Manual Circuit Routing
•For point-to-point (straight) Ethernet circuits, only VC endpoints can be specified as multiple
sources or drops.
For bidirectional circuits, CTC creates an SNCP connection at the source node that allows traffic to be
selected from one of the two sources on the ONS 15454 SDH network. If you check the Fully Path
Protected option during circuit creation, traffic is protected within the ONS 15454 SDH network. At the
destination, another SNCP connection is created to bridge traffic from the ONS 15454 SDH network to
the two destinations. A similar but opposite path exists for the reverse traffic flowing from the
destinations to the sources. For unidirectional circuits, an SNCP drop-and-continue connection is created
at the source node.
10.12 Manual Circuit Routing
Routing circuits manually allows you to:
•Choose a specific path, not necessarily the shortest path.
•Choose a specific VC4/VC3/TUG3/TUG2/VC12 on each link along th e route.
•Create a shared packet ring for multicard EtherSwitch circuits.
•Choose a protected path for multicard EtherSwitch circuits, allowing virtual SNCP segments.
CTC imposes the following rules on manual routes:
•All circuits, except multicard EtherSwitch circuits in a shared packet ring, should have links with a
direction that flows from source to destination. This is true for multicard EtherSwitch circuits that
are not in a shared packet ring.
•If you enabled Fully Path Protected, choose a diverse protect (alternate) path for every unprotected
segment (Figure 10-7).
Figure10-7 Alternate Paths for Virtual SNCP Segments
•For multicard EtherSwitch circuits, the Fully Path Protected option is ignored.
•For a node that has an SNCP selector based on the links chosen, the input links to the SNCP selectors
cannot be 1+1 or MS-SPRing protected (Figure 10-8). The same rule applies at the SNCP bridge.
83949
MS-SPRing
1+1 1+1
1+1
Two way Two way
Two way Two way
Node 8Node 7
Node 5 Node 6
SNCP SNCP
Two wayTwo way
Node 4Node 3
Node 1 Node 2
Two way
Node 12Node 11
Node 9 Node 10
Source
Path Segment 1
SNCP/mesh
protected
Needs alternate path
from N1 to N2
Drop
Path Segment 3
MS-SPRing protected
Path Segment 2
1+1 protected
Path Segment 4
1+1 protected
No need for alternate path